[Codegen][X86] Fix /hotpatch with clang-cl and inline asm

llvm/lib/Target/X86/X86MCInstLower.cpp

@@ -980,8 +980,10 @@ void X86AsmPrinter::LowerPATCHABLE_OP(const MachineInstr &MI,
   SmallString<256> Code;
   unsigned MinSize = MI.getOperand(0).getImm();
 
-  if (NextMI != MI.getParent()->end()) {
+  if (NextMI != MI.getParent()->end() && !NextMI->isInlineAsm()) {
     // Lower the next MachineInstr to find its byte size.
+    // If the next instruction is inline assembly, we skip lowering it for now,
+    // and assume we should always generate NOPs.
     MCInst MCI;
     MCIL.Lower(&*NextMI, MCI);
 

llvm/test/CodeGen/X86/patchable-prologue.ll

@@ -193,3 +193,20 @@ do.body:                                          ; preds = %do.body, %entry
 do.end:                                           ; preds = %do.body
   ret void
 }
+
+
+; Test that inline asm is properly hotpatched. We currently don't examine the
+; asm instruction when printing it, thus we always emit patching NOPs.
+
+; 64: inline_asm:
+; 64-NEXT: # %bb.0:
+; 64-NEXT: xchgw   %ax, %ax                        # encoding: [0x66,0x90]
+; 64-NEXT: #APP
+; 64-NEXT: nop                                     # encoding: [0x90]
+; 64-NEXT: #NO_APP
+
+define dso_local void @inline_asm() "patchable-function"="prologue-short-redirect" {
+entry:
+  call void asm sideeffect "nop", "~{dirflag},~{fpsr},~{flags}"()
+  ret void
+}